EVAL-ADE7753EB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADE7753EB' PDF : 38 Pages View PDF
ADE7753
From Equation 19 it can be seen that there is a small ripple in
the energy calculation due to a sin(2 ωt) component. This is
shown graphically in Figure 68. The active energy calculation is
shown by the dashed straight line and is equal to V × I × t. The
sinusoidal ripple in the active energy calculation is also shown.
Since the average value of a sinusoid is 0, this ripple does not
contribute to the energy calculation over time. However, the
ripple can be observed in the frequency output, especially at
higher output frequencies. The ripple gets larger as a percentage
of the frequency at larger loads and higher output frequencies.
The reason is simply that at higher output frequencies the
integration or averaging time in the energy-to-frequency
conversion process is shorter. As a consequence, some of the
sinusoidal ripple is observable in the frequency output. Choosing
a lower output frequency at CF for calibration can significantly
reduce the ripple. Also, averaging the output frequency by using
a longer gate time for the counter achieves the same results.
E(t)
Vlt
–
VI
4×π×fL(1+2×fL/8. 9Hz )
sin(4×π×fL×t)
t
02875-0-067
Figure 68. Output Frequency Ripple
OUTPUT
FROM
LPF2
WGAIN[11:0]
++
48
%
APOS[15:0]
WDIV[7:0]
FROM
CHANNEL 2
ADC
LPF1
ZERO CROSS
DETECTION
CALIBRATION
CONTROL
23
0
LAENERGY [23:0]
0
ACCUMULATE ACTIVE
ENERGY IN INTERNAL
REGISTER AND UPDATE
THE LAENERGY REGISTER
AT THE END OF LINECYC
LINE CYCLES
LINECYC [15:0]
Figure 69. Energy Calculation Line Cycle Energy Accumulation Mode
02875-0-068
Rev. C | Page 32 of 60
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